In 2006, the Radio-communication sector of the International Telecommunications Union (ITU-R) officially named the Beyond Third Generation (B3G) in mobile communication system, also called the fourth generation mobile communication, technologies as International Mobile Telecommunications-Advanced (IMT-Advanced) technologies. The IMT-Advanced technologies require realization of a higher data rate and larger system capacity, a target peak rate is: above 1 gigabit per second (Gbps) for slowly moving in hotspot coverage scenarios; 100 megabits per second (Mbps) for fast moving in wide-area coverage scenarios.
Currently, standards organizations, including the 3rd Generation Partnership Project (3GPP) standards organization, are conducting research on the IMT-Advanced officially or unofficially. The Long Term Evolution (LTE) technologies being standardized by the 3GPP have shown technical characteristics of the IMT-Advanced, and the 3GPP is going to further evolve the LTE to the LTE-Advanced (LTE-A) technologies.
On one hand, an IMT-Advanced system puts forward high requirements on system capacity; however, on the other hand, a large bandwidth spectrum sufficient for supporting high capacity can only be found in high frequency bands, and path loss and penetration loss of the high frequency band are huge, so that excellent coverage cannot be achieved. In order to meet capacity requirements of the IMT-Advanced, currently relay is taken as a candidate technology in LTE-A for improving the system capacity and coverage for research.
In so-called relay technologies, taking a simple two-hop relay for example, a wireless link between an evolved NodeB (eNB) and a User Equipment (UE) is split into two links: a wireless link between the eNB and a Relay Node (RN) and a wireless link between the RN and the UE, thereby providing a chance of replacing a low quality link with two high quality links to achieve higher link capacity and better coverage.
In an LTE radio network, definitions of mainly involved interfaces are as follows.
A Un interface is an interface between a relay and a serving eNB of the relay.
A Uu interface is an interface between a UE and a serving relay of the UE.
An S1 interface is an interface between a Mobility Management Entity (MME)/Serving Gateway (S-GW) and an eNB.
An X2 interface is an interface between eNBs.
In the LTE radio network, a service of a UE is mapped to a Data Radio Bearer (DRB) at a Uu interface, and an eNB can identify a DRB of data and perform proper processing on the data. In an LTE-A relay network, RNs, for example type-1 relays, access the network through an eNB. The RN supports an LTE UE, and from the LTE UE viewpoint the RN and the LTE eNB are the same in functions.
The prior art provides an LTE-A relay protocol architecture, if a Un interface uses an S1 message, an eNB uses an S1 message on an Evolved Packet Core (EPC) network side; if the Un interface uses an X2 message, the eNB uses an X2 message on the EPC network side.
The process is described below by using an example in which in a UE handover process a relay uses an S1 message to initiate a handover request message to an eNB.
After receiving the handover request message (S1-AP: HO required message) of an S1 interface, the eNB may only modify a UE S1 application protocol identifier (S1AP UE ID), and does not modify other parts, so as to forward the S1 handover request message (S1AP: HO required message) to an MME to perform corresponding S1 handover procedures. Herein, the S1-AP or S1AP stands for S1 Application Protocol.
Or similarly, the eNB receives a Radio Resource Control (RRC) message carrying contents of the S1 handover request message, and after parsing the S1 message the eNB initiates corresponding S1 handover procedures on a core network side. Accordingly, for an X2 message, if the eNB receives an RRC message carrying contents of an X2 handover request message, and after parsing the X2 message the eNB initiates corresponding X2 handover procedures.
During the implementation of the present invention, the inventors find that the prior art at least has the following defects.
The X2 interface and the S1 interface cannot be flexibly used, so that message contents may not be transmitted smoothly. For example, during a UE handover process, when an RN sends an X2 message to a source eNB at a Un interface, the source eNB uses an X2 message to send information to a target eNB accordingly, thereby resulting in an inflexible signaling transfer manner.